Sketcher: General bug fix: Tangency wrongly suggested

What?
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- On creation of a shape autoconstraints are suggested.
- Tangent autoconstraint was suggested even with lines perpendicular to the tangency direction

Reproduce
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- Make a circle on the origin and move the mouse along the X axis, it will suggest a tangency that is impossible
- Click on the axis and no circle will be created

Solution
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- The SeekConstraint now can use the parameter dir to give a direction that is substantially perpendicular to the expected tangency, so that
if an object having a direction (a line) is hit, a tangency will not be suggested if within around 6 degrees of being parallel.
- Additionally, if such a line is an X,Y axis of the sketch, tangency will only be suggested if the direction is within 6 degrees of being perpendicular (i.e. it is almost tangent already while sketching).
- This difference is due to the fact that an X or Y axis can not "move" to meet the object under creation, whereas a line can.